Even at idle you should be able to suck a rag to the front of the radiator if it doesn't you need to figure out what it will take to draw more air thru it. If your top hose was 221 and bottom was 220 you are not cooing the water at all.
Per post #33, it was 221/210
Never-the-less 11 degrees says it all.
My 1973 26" A/C rad manages a bit over 30 degrees. And it cools very well. ir3333 in post #33 stated to expect 45/50* "delta-T"